Amazon is limiting the number of single, low-priced items shoppers can purchase in an effort to offset rising costs. Amazon is raising transportation fees for suppliers of beverages, diapers and other heavy, bulky products that are expensive to ship, which in turn is set to make it harder for shoppers to buy small orders of toothbrushes, soap, lipstick and other inexpensive items that are difficult to sell profitably online unless they’re part of a larger purchase.